Abstract

Objectives: SNCG is a novel prognostic biomarker in UPSC. We have shown that its overexpression correlates with aggressive cellular properties and resistance to paclitaxel in a UPSC cell line (SPEC2) as well as poor prognosis in a pilot set of UPSC patients. The goal of this study was to determine the mechanism of SNCG-associated taxane resistance by evaluating the effect of SNCG on the mitotic checkpoint and its propensity to modulate extracellular signal-regulated protein kinase 1/2 (ERK 1/2) signaling pathways.

Methods: A stably transfected SPEC2 cell line was created using shSNCG versus shControl oligonucleotides. Similarly, Ishikawa cells were transiently transfected with an SNCG expression vector versus empty vector. Differences in cell proliferation were measured using a cell viability assay and BrdU incorporation assay after treatment with paclitaxel. Cell cycle analysis was used to study the effect of SNCG on the mitotic checkpoint. Differences in expression of the checkpoint kinase BubR1 due to SNCG were studied using real time PCR, Western blot, 26S ubiquitin-proteasome inhibition, and siRNA to BubR1. ERK and phospho-ERK levels were measured in SPEC2 cells with and without SNCG expression by Western blot. SPEC2 cells were treated with paclitaxel with and without the MEK inhibitor UO126 and apoptosis was measured using cleaved PARP analysis.

Conclusions: SNCG overexpression in UPSC leads to taxane resistance by interacting with the mitotic checkpoint kinase BubR1 causing its degradation. SNCG is also associated with sustained ERK activation. Targeting SNCG in conjunction with MEK inhibition may represent a novel therapeutic strategy to overcome taxane resistance in these cells.